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Few questions about PMDG 737-800


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53 replies to this topic

#1 nicholas49

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Posted 17 February 2012 - 04:16 AM

HelloI am wondering if some kind person can help me with a few 'teething' problems I'm having with the PMDG 737-800.1) Rejected take-offs: they don't happen! With the autobrakes set to RTO, if I knock out the A/T and bring the thrust levers to idle on the take-off roll (yes, above eighty knots), the aircraft does not perform an RTO. Have I not configured something correctly here? Why does the RTO function not work?2) I have loaded a route into the FMC from FS Build. I have programmed the aircraft weight, V speeds etc. correctly. I spool up the engines manually to 40%, then I select TOGA thrust. So far, so good. But when I rotate the aircraft and follow the FD, the speed starts to decay. This is, obviously, extremely dangerous (in real life, at least), so I imagine that I must have overlooked something fundamental / overlooked an FMC setting if this happens?3) On a similar note, what speed should I select in the IAS/MACH box on the MCP before take-off? Is it the V2 speed? Is it 250 knots? Let's assume there are no restrictions for the sake of argument. What do you guys recommend? Again, looking for a smooth acceleration.4) How do I know which departure profile to select from FS Build without having the plates to hand and 'knowing' which ones are used for which routes? Does anyone have any tips here?5) I understand there is a good tutorial for this aircraft by Tim (?). Can anyone direct me to this?In summary, my main problem is managing a smooth climb-out with appropriate acceleration. Probably something that takes the professionals a LOT of time to practise, and here I am asking for quick solutions :) Thank you so much for your help.Best wishesNick

Edited by nicholas49, 17 February 2012 - 04:20 AM.


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#2 PHXMD-11

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Posted 17 February 2012 - 04:40 AM

1. I do believe you have to throw the engines into reverse. That may kick in the autobrakes.2.Have you set the flaps correctly? I would just keep the Vspeeds as they are. I don't own FSBuild but the numbers could be off.3.Set V2 in the IAS/Mach window.4. Again I don't own FSBuild so I don't know.5. The tutorial is on AVSIM. Just search for "737 NGX tutorial".

Kenny Lee
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#3 Avroboeing

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Posted 17 February 2012 - 05:12 AM

1. I do believe you have to throw the engines into reverse. That may kick in the autobrakes. Yep.2.Have you set the flaps correctly? I would just keep the Vspeeds as they are. I don't own FSBuild but the numbers could be off. I second this statement. I noticed this as well. I don't know what the procedure is, so thanks for bringing this up. My technique is to take off without FD engaged (for a ZFW of above 45 tonne), and takeoff with enough positive pitch to maintain an airspeed greater than V2 until I reach 1500ft, then I engage FD, LNAV and VNAV (if flying a SID) or LNAV and Heading Select (when flying ATC RADAR Vectors).3.Set V2 in the IAS/Mach window. I second this too. It's in the manuals too.4. Again I don't own FSBuild so I don't know. Enter your departure, and destination data, then click on "PM" which is next to the destination box. Now, you'll see on the right hand side of the screen, the names of the SID's and STAR's for your dep and arr runways. If you click on one, it will draw it on the map for you. Click "PM" again, and then build your plan. Don't forget to select your SID and STAR again in the drop down boxes.5. The tutorial is on AVSIM. Just search for "737 NGX tutorial". Yep.

Ash Frew.

#4 albix

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Posted 17 February 2012 - 05:24 AM

Kenny,RTO - automatically applies maximum brake pressure when Thrust Levers are retarded to Idle at or above 90 knots.

#5 nicholas49

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Posted 17 February 2012 - 05:34 AM

Thanks for the replies. To follow-up a couple of points:1. I am not convinced that you should need to select reverse thrust to get the autobrakes to work. I actually just tried another RTO and this time the autobrakes engaged, so maybe it was a glitch before (just as well it's not a real aircraft, eh?).2. Flaps. The aircraft's flap setting matches what is programmed in the FMC (i.e. Flaps 5). So this should not be the reason why the FMC does not provide the correct climb-out performance data for the FD. However, this point raises another question: how do I know which flap setting I need for any particular departure? Where do I source this information?I do not agree that you should need to take-off without the FD engaged to overcome the speed decay problem (although I accept that not using the FD is one possibility). To clarify: my question relates specifically to operations using the FD and FMC, so if someone can explain why following the FD after take-off leads to a speed decay, I would still be grateful to hear it. Something is not right here.One additional question I have: at what altitude should I engage LNAV?3. Fine. But does this not mean that the aircraft will stop accelerating at V2?4. Thanks-I will try that!5. Thanks.Nick

Edited by nicholas49, 17 February 2012 - 05:40 AM.


#6 El padrino

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Posted 17 February 2012 - 05:55 AM

Thanks for the replies. To follow-up a couple of points:1. I am not convinced that you should need to select reverse thrust to get the autobrakes to work. I actually just tried another RTO and this time the autobrakes engaged, so maybe it was a glitch before (just as well it's not a real aircraft, eh?).2. Flaps. The aircraft's flap setting matches what is programmed in the FMC (i.e. Flaps 5). So this should not be the reason why the FMC does not provide the correct climb-out performance data for the FD. However, this point raises another question: how do I know which flap setting I need for any particular departure? Where do I source this information?I do not agree that you should need to take-off without the FD engaged to overcome the speed decay problem (although I accept that not using the FD is one possibility). To clarify: my question relates specifically to operations using the FD and FMC, so if someone can explain why following the FD after take-off leads to a speed decay, I would still be grateful to hear it. Something is not right here.One additional question I have: at what altitude should I engage LNAV?3. Fine. But does this not mean that the aircraft will stop accelerating at V2?4. Thanks-I will try that!5. Thanks.Nick

2. There's a payware add-on named TOPCAT that provides such info otherwise it's probably some kind of complicated calculation with the use of performance tables etc. Tedious I think, at least for my simming style... LNAV can be armed on ground but Autopilot should be engaged at min 400ft above ground level.3. The FD will command a pitch that will lead to a V2+20 speed and not V2. If you set your FMC properly and engage VNAV then the FD will adjust pitch as required (lower above acceleration altitude, go faster than 250kts above 10,000ft etc).Flying with FD off is not the best of ideas I think. I'm more than 100% sure that a proprely set-up FMC will be more accurate than the average simmer, especially if you think that the sim does not provide any physical feedback on your body and you only rely on your eyes and your instruments, which is not always always easy to do.
George Golas
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#7 Avroboeing

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Posted 17 February 2012 - 06:31 AM

I stand corrected... And no problems. I don't read the manuals, and hate advising others to, but I think in this situation you/I would be better off in doing so. Anyway...I just tried flying to the FD command bars, and was able to see my speed decay as reported. Would love clarification from someone more learned on the subject on how to deal with it.Night guys.Ash Frew.

Edited by Avroboeing, 17 February 2012 - 06:37 AM.


#8 Nixon

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Posted 17 February 2012 - 09:17 AM

Hi. speed will decay after take off if you rotate too slowly so that you get an initial speed increase above the bugged speed, then the FD's will command a pitch up to reduce to the required speed.
Regards
Nixon Thomas

#9 Daniel choen

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Posted 17 February 2012 - 10:17 AM

HelloI am wondering if some kind person can help me with a few 'teething' problems I'm having with the PMDG 737-800.1) Rejected take-offs: they don't happen! With the autobrakes set to RTO, if I knock out the A/T and bring the thrust levers to idle on the take-off roll (yes, above eighty knots), the aircraft does not perform an RTO. Have I not configured something correctly here? Why does the RTO function not work?2) I have loaded a route into the FMC from FS Build. I have programmed the aircraft weight, V speeds etc. correctly. I spool up the engines manually to 40%, then I select TOGA thrust. So far, so good. But when I rotate the aircraft and follow the FD, the speed starts to decay. This is, obviously, extremely dangerous (in real life, at least), so I imagine that I must have overlooked something fundamental / overlooked an FMC setting if this happens?3) On a similar note, what speed should I select in the IAS/MACH box on the MCP before take-off? Is it the V2 speed? Is it 250 knots? Let's assume there are no restrictions for the sake of argument. What do you guys recommend? Again, looking for a smooth acceleration.4) How do I know which departure profile to select from FS Build without having the plates to hand and 'knowing' which ones are used for which routes? Does anyone have any tips here?5) I understand there is a good tutorial for this aircraft by Tim (?). Can anyone direct me to this?In summary, my main problem is managing a smooth climb-out with appropriate acceleration. Probably something that takes the professionals a LOT of time to practise, and here I am asking for quick solutions :)Thank you so much for your help.Best wishesNick

1. RTO takeoff will occur at 90 and above not above V1!! v1 is the latest time you can perform a RTO (from real pilot resource)2.i have no Idea as i am not using fsbuild.3. you should put the V2 speed as someone else mentioned this will automatically will increase to V2+20, i highly recommend the TOPcat for calculation, i recently bought it, and it's one amazing program!4.depends, are you flying online?5.as someone else mentioned at avsimhave a great time with the beauty!

Edited by Daniel choen, 17 February 2012 - 10:18 AM.

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#10 nicholas49

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Posted 17 February 2012 - 10:25 AM

Thanks for the replies everyone.

LNAV can be armed on ground but Autopilot should be engaged at min 400ft above ground level.

This is another problem I am having. The MCP will not let me arm LNAV on the ground. It will however activate once airborne. Is this because something is not right in the FMC? Does anyone else experience this? It means that you take-off with the autopilot not in the correct setting (I think it defaults to HDG).If I select V2 in the IAS/MACH display, at what point do you start commanding the autopilot to accelerate to 250 knots below 10,000? I don't understand when you start making manual changes to the autopilot's commanded speed.

#11 Daniel choen

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Posted 17 February 2012 - 10:28 AM

LNAV can be armed on ground but Autopilot should be engaged at min 400ft above ground level.

acutally autopilot can be engaged at 800ft, Lnav at 400ft,.
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#12 Daniel choen

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Posted 17 February 2012 - 10:33 AM

Thanks for the replies everyone.This is another problem I am having. The MCP will not let me arm LNAV on the ground. It will however activate once airborne. Is this because something is not right in the FMC? Does anyone else experience this? It means that you take-off with the autopilot not in the correct setting (I think it defaults to HDG).If I select V2 in the IAS/MACH display, at what point do you start commanding the autopilot to accelerate to 250 knots below 10,000? I don't understand when you start making manual changes to the autopilot's commanded speed.

it's possible to arm the LNAV if you'r 5 miles from the first waypoint, or something like that, so it's possible that you did not select the correct departure route.and for the autopilot procedures, after you arm the VNAV the plane will reach to the acceleration height and then it'll start to accelerate, if the plane is flying on VNAV it'll do all automatically, just don't forget to set the mcp altitude and it'll automatically reach to the altitude according to the route that you selected. cheers, BTW of some one can explain it better then me please do it, as i am not the best at explanations. LOL..
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#13 El padrino

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Posted 17 February 2012 - 01:26 PM

acutally autopilot can be engaged at 800ft, Lnav at 400ft,.

800ft might be don't remember, but LNAV cannot be engaged before the AP is. It can be armed though.
George Golas
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#14 adamant365

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Posted 17 February 2012 - 02:24 PM

Arming LNAV on the ground is possible but the first waypoint must be +/- 5 degrees of runway heading. If armed on the ground, LNAV will certainly engage at 400 ft. It doesn't matter if the A/P is on or off. You simply have to fly the FD to follow the LNAV commands yourself.

Adam Hill


#15 Barbs

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Posted 18 February 2012 - 12:38 AM

Hi,Ignore the performance figures given by FSBuild. The takeoff speeds given by the FMC will be more accurate. Also, I don't usually include the departure and approach procedures in the FSBuild flight plan for that reason (you may not get that departure) but I will add some fuel (a few hundred kilos) to account for manuevering (this is known as a departure pad or arrival pad).The decay in speed you are experiencing is suspect may be happening at acceleration height (usually around 1000ft AFE) when the throttles come back slightly and you are still maintaining 15deg pitch, without more info I couldn't tell for sure. Here is a correct although very truncated procedure (different airlines may do it slightly differently like arming different modes, but this should get you in the air without a fuss):- Set V2 in the MCP window.- Arm LNAV (if applicable. See above for criteria on arming of LNAV on the ground. Note if you don't have a roll mode armed, the FD will either command HDG SEL or WINGS LEVEL depending on the options selected in the CDU).- Arm A/T.- Throttles to 40% N1.- TOGA- Vr rotate smoothly to 15deg nose up (should take approx 3 seconds).- Follow FD bars to maintain V2+10-20kts initially.- At Accel Height confirm CLB thrust (CLB appears in green above the engine guages and you will hear the engines throttle back a little)- At this stage select Flaps Up speed in the MCP speed window (the magenta bug on the speed tape, move it to the -UP flag).- This will cause the FD to command a slight nose down to allow the a/c to accelerate, follow it.- Retract flaps on schedule.- After Flaps Up selected, set 250kts or take VNAV.- CMA A or B can be taken at any time during this procedure after 400ft AGL. But make sure your are on the flight director bars and trimmed properly before you do this for a smoother flight profile.- Congrats, you're away!

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